U.S. patent number 7,776,559 [Application Number 10/762,784] was granted by the patent office on 2010-08-17 for disposable blood test device.
This patent grant is currently assigned to Hewlett-Packard Development Company, L.P.. Invention is credited to Winthrop D. Childers, David Tyvoll.
United States Patent |
7,776,559 |
Childers , et al. |
August 17, 2010 |
Disposable blood test device
Abstract
A disposable blood test device comprises a substrate configured
for carrying a chemical reagent and circuitry formed on the
substrate. The circuitry comprises a sensor portion associated with
the chemical reagent to enable measurement of at least one of a
presence and a concentration of a blood analyte, and an information
storage portion configured to store information indicative of a
property of the chemical reagent.
Inventors: |
Childers; Winthrop D. (San
Diego, CA), Tyvoll; David (La Jolla, CA) |
Assignee: |
Hewlett-Packard Development
Company, L.P. (Houston, TX)
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Family
ID: |
34794928 |
Appl.
No.: |
10/762,784 |
Filed: |
January 22, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050163657 A1 |
Jul 28, 2005 |
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Current U.S.
Class: |
435/7.21;
435/287.1; 436/149; 429/92; 435/174; 435/283.1; 435/7.25; 435/7.24;
436/518 |
Current CPC
Class: |
A61B
5/1486 (20130101); G01N 33/48771 (20130101); A61B
5/14532 (20130101); A61B 2562/085 (20130101) |
Current International
Class: |
G01N
33/567 (20060101) |
Field of
Search: |
;422/50,68.1,82.01,98
;435/4,287.1,287.9 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2 332 943 |
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Jul 1999 |
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GB |
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WO 2004/113915 |
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Dec 2004 |
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WO |
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Other References
i-STAT, Product Info-Cartridges, 6 pages,
<www.istat.com/products/cartridges.asp>, 2001. cited by other
.
i-STAT, Microfluidic and Biosensor Chip Technology, 3 pages,
<www.istat.com/products/docs/biosenso.pdf>, last available
2002. cited by other.
|
Primary Examiner: Yang; Nelson
Claims
What is claimed is:
1. A self-calibrating, disposable blood test device insertable in a
meter, the test device comprising: a substrate configured for
carrying a chemical reagent; and circuitry formed on the substrate,
the circuitry comprising: a sensor portion associated with the
chemical reagent to enable measurement of at least one of a
presence and a concentration of a blood analyte, the sensor portion
including an electrode sensor; an input/output pad connected to the
electrode sensor; and an additional input/output pad connected to
an information storage portion that is connected in parallel with
the electrode sensor; wherein the information storage portion is
configured to store information indicative of a property of the
chemical reagent for calibration of the meter, the information
storage portion including a plurality of impedance elements
including at least one of: a plurality of inductors arranged in
series; or a plurality of capacitors arranged in parallel, wherein
each impedance element includes a region that may be physically
altered by at least one of punching, drilling, or shorting via
fusible link, to create a short circuit or open circuit, in order
to activate or deactivate the impedance element wherein the
information is stored by activating or deactivating a select number
of the impedance elements in a determinable order, which creates a
characteristic impedance between the input/output pad and the
additional input/output pad that is measurable by the meter and
which corresponds to at least one calibration value that is
indicative of the property of the chemical reagent; and wherein the
impedance elements within the information storage portion are
arranged such that 2.sup.N different potential characteristic
impedances may be produced, wherein N is the number of impedance
elements.
2. The test device of claim 1, wherein the test device comprises
one of a set of test devices with the information storage portion
of each test device storing substantially the same information in
the information storage portion to be indicative of the at least
one calibration value of the chemical reagent for the set of test
devices.
3. The test device of claim 1, wherein the circuitry of the
substrate comprises a semiconductor portion and the circuitry
defines a non-volatile memory configured to store the
information.
4. The test device of claim 3, further comprising an electrical
signal generator external to the test device and configured to send
an electrical signal to the non-volatile memory to cause storage of
the information in the information storage portion of the test
device.
5. The test device of claim 3, wherein the non-volatile memory is
configured to also store at least one of a date of manufacture, an
operating characteristic, and serial number.
6. A method of manufacturing a test device insertable in a meter
for the detection of a blood analyte, the method comprising:
forming circuitry on a substrate of the test device, the substrate
configured for carrying a chemical reagent, and the circuitry
including: a sensor portion associated with the chemical reagent to
enable measurement of at least one of a presence and a
concentration of a blood analyte, the sensor portion including an
electrode sensor; an input/output pad connected to the electrode
sensor; and an additional input/output pad connected to an
information storage portion that is connected in parallel with the
electrode sensor; wherein the information storage portion is
configured to store information indicative of a property of the
chemical reagent for calibration of the meter, the information
storage portion including a plurality of impedance elements
including at least one of: a plurality of inductors arranged in
series; or a plurality of capacitors arranged in parallel, wherein
each impedance element includes a region that may be physically
altered by at least one of punching, drilling, or shorting via
fusible link, to create a short circuit or open circuit, in order
to activate or deactivate the impedance element depositing the
chemical reagent on the sensor portion that enables detection of
the blood analyte; and storing information in the information
storage portion; wherein the information is stored by activating or
deactivating a select number of the impedance elements in a
determinable order, which creates a characteristic impedance
between the input/output pad and the additional input/output pad
that is measurable by the meter and which corresponds to at least
one calibration value that is indicative of the property of the
chemical reagent; and wherein the impedance elements within the
information storage portion are arranged such that 2.sup.N
different potential characteristic impedances may be produced,
wherein N is the number of impedance elements.
7. The method of claim 6, further comprising: determining a
property of the test device, the property of the test device being
selected from the at least one calibration value of the chemical
reagent, a date of manufacture, an analyte array identifier, and an
operating characteristic.
8. The method of claim 7, wherein storing information in the
information storage portion comprises storing at least one of the
at least one calibration value of the chemical reagent, the date of
manufacture, the analyte array identifier, and the operating
characteristic.
9. The method of claim 6, wherein forming the information storage
portion of the circuitry comprises forming a thin film circuitry
portion on the substrate that defines a non-volatile memory
portion, and wherein storing information in the information storage
portion comprises sending an electrical signal to the information
storage portion to store a value in the non-volatile memory
portion.
10. The method of claim 6, further comprising: measuring the at
least one calibration value of the chemical reagent to determine a
calibration factor for the test device; wherein storing information
in the information storage portion comprises altering at least one
of the plurality of impedance elements, wherein the number of
altered impedance elements is indicative of the calibration factor
of the test device.
11. The method of claim 10, wherein altering the plurality of
impedance elements comprises disabling at least one of the
plurality of impedance elements by at least one of physically
removing a conductive portion of the impedance element and
physically adding a conductive portion to the impedance
element.
12. The test strip of claim 1, wherein the information storage
portion is inseparable from the disposable test strip.
13. The test device of claim 1 wherein: the electrode sensor
includes first and second electrode sensors; the input/output pad
includes: a first input/output pad connected to the first electrode
sensor; and a second input/output pad connected to the second
electrode sensor; and the characteristic impedance is created
between the second input/output pad and the additional input/output
pad.
Description
BACKGROUND
Millions of people across the globe face the daily challenge of
managing their diabetes. Several times a day, they must test their
blood for glucose levels. Currently, most consumers monitor their
daily glucose levels by themselves through the use of
electrochemical glucose meters. In these devices, a sample of blood
is collected from a pin prick in the body into a test strip, which
is inserted into a meter for calculation and display of the glucose
level. The longevity and health of diabetics is directly related to
how tightly their glucose levels are controlled through daily
self-testing and administration of insulin, as well as diet and
exercise. Accordingly, highly accurate glucose testing in
self-monitoring can aid millions of diabetics who daily endeavor to
maintain optimal blood glucose levels.
Moreover, since blood is a vital component of the body, many other
blood analytes are of significant interest in managing human
health. Accordingly, self-testing or measuring other analytes or
properties of blood are also of interest as the medical industry
seeks rapid and effective methods to monitor various medical
conditions.
Disposable test strips used in self-testing must be calibrated to
the meter with which they are used. In particular, these test
strips include several chemical reagents for reaction with the
blood sample to enable detection of a particular blood analyte.
Since each set of test strips has a slightly different chemical
composition, each set of test strips must be calibrated relative to
the meter into which the test strips are inserted. Unfortunately,
conventional calibration mechanisms do not provide a robust method
for reliable and accurate calibration of test strips with
meters.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a blood analyzer system, according
to an embodiment of the present invention.
FIG. 2 is a schematic illustration of a blood analyzer system,
according to an embodiment of the present invention.
FIG. 3 is block diagram of a method of manufacturing a test strip,
according to an embodiment of the present invention.
FIG. 4 is a top plan view of a test strip, according to an
embodiment of the present invention.
FIG. 5 is a table illustrating parameters of an information storage
device, according to an embodiment of the present invention.
FIG. 6 is plan view schematically illustrating an information
storage device, according to an embodiment of the present
invention.
FIG. 7 is plan view schematically illustrating another information
storage device, according to an embodiment of the present
invention.
FIG. 8 is a schematic block diagram of another test strip system,
according to an embodiment of the present invention.
DETAILED DESCRIPTION
In the following detailed description, reference is made to the
accompanying drawings which form a part hereof, and in which is
shown by way of illustration specific embodiments in which the
invention may be practiced. In this regard, directional
terminology, such as "top," "bottom," "front," "back," "leading,"
"trailing," etc., is used with reference to the orientation of the
Figure(s) being described. Because components of embodiments of the
present invention can be positioned in a number of different
orientations, the directional terminology is used for purposes of
illustration and is in no way limiting. It is to be understood that
other embodiments may be utilized and structural or logical changes
may be made without departing from the scope of the present
invention. The following detailed description, therefore, is not to
be taken in a limiting sense, and the scope of the present
invention is defined by the appended claims.
Embodiments of the present invention are directed to a method for
analyzing blood to detect an analyte or to determine a property of
the blood. An analyte is any substance within a blood sample that
is selected for detection. One blood analyte that can be measured
indirectly through an electrochemical test includes glucose. In
these tests, a sample of blood is exposed within a test strip to
enzyme reagents for reaction with the glucose in the blood sample.
The reaction products from the interaction of the blood glucose
with the enzymes further interact with mediators and electrode
sensors within the test strip as part of an electrochemical
reaction. Based upon a measurement of current or charge at the
electrode sensors from that electrochemical reaction, an indirect
measurement of glucose concentration in the blood sample is
obtained. Alternatively, the reaction products of the
glucose-enzyme interaction are measured through reflectance
photometry to indirectly determine a glucose level.
Embodiments of the present invention are directed to automatically
calibrating disposable analyte test devices relative to a meter in
which the test devices are inserted. Each disposable test device
comprises calibration information that is electronically stored in
the test device so that the calibration information is inseparable
from the test device and electrically communicated to the meter,
without any additional steps by the user, upon insertion into the
meter. The calibration information comprises, but is not limited
to, a value indicative of a property of a chemical reagent on the
test device.
In one embodiment of the present invention, a disposable test
device enables measuring a blood analyte. The test device comprises
a substrate, circuitry, and a chemical reagent. The substrate
carries the chemical reagent and is configured for receiving a
blood sample. The circuitry is formed on the substrate and
comprises a sensor portion and an information storage portion. The
sensor portion is associated with a chemical reagent to enable
measurement of a blood analyte in the blood sample. The information
storage portion is configured to store calibration information
about a property of the test device.
These properties of the test device may include, but are not
limited to, information indicative of a property of the chemical
reagent, a date of manufacture, and/or optimal operating electrical
characteristics for the sensor portion, etc. For example, in some
embodiments, a property of the test device (that is stored as part
of the calibration information) can comprise a physical or
electrical property of the test device, such as a geometry, sizes,
and/or spacing of sensor electrodes on the test device.
Embodiments of the present invention can be applied for detection
or measurement of many blood analytes other than glucose. Other
common analytes of interest include, for example, markers for
cardiovascular disease, drugs, illicit drugs, antibiotics, and
antigens and toxins associated with infectious organisms. These
analytes include, but are not limited to, troponins, b-type
natriuretic peptide, clostridium difficile toxins, digitoxin,
digoxin, theophylline, warfarin, barbiturates, methadone,
amphetamine and amphetamine analogues, propoxyphene, opiates,
cocaine, tetrahydrocannabinol, benzodiazepines, phencyclidine,
gentamicin, vancomycin, acetyl choline, amylase, bilirubin,
cholesterol, chorionic gonadotropin, creatine kinase, creatine,
RNA, DNA, fructosamine, glutamine, hormones, ketones, lactate,
peroxide, prostate-specific antigen, prothrombin, thyroid
stimulating hormone, and their metabolites. U.S. Pat. No. 6,281,006
discloses methods to determine the concentration of RNA and
DNA.
In one embodiment shown in FIG. 1, system 10 is directed to testing
blood properties, such as blood glucose levels, in blood sample 18
taken from a finger 16 or other body part of a human subject.
System 10 comprises meter or receiving portion 12 and test device
14 (e.g., a test strip). Meter 12 is generally a handheld-type
glucose meter used by patients to assist in self-monitoring their
glucose levels. However, meter 12 is not precluded from being used
to measure and monitor other analytes and properties of blood
obtained and detected via a test strip. Moreover, meter 12 also can
comprise a countertop testing device rather than a handheld
device.
Test device 14 is removably insertable into a portion of meter 12
and is part of a set 15 of test devices 14. Each test device 14
comprises fluid pathway 40, chamber 41, sensor (S) 42, reagent (R)
44, calibration information (C) 46, and input/output contacts
48.
Test device 14 receives blood sample 18 via fluid pathway 40, which
pulls blood sample 18 into chamber 41 via capillary fluid action
through a combination of the fluid properties of blood and the
dimensions, shape, and surface properties of pathway 40. Chamber 41
comprises a test surface with one or more enzyme or immunoassay
reagents (R) 44 suitable for causing a chemical reaction or
immunorecognition with an analyte in blood sample 18. This
interaction creates a reaction product to enable indirect
measurement of a blood analyte via an electrochemical or
immunorecognition detection method. Calibration information (C) 46
represents one or more parameters affecting the performance of test
device 14 with meter 12. For example, calibration information (C)
46 corresponds to one or more properties of test device 14, such as
a calibration characteristic of the reagents (R) 44, a date of
manufacture, meter operating characteristics with test device 14
(e.g., frequency, voltage, etc.), and/or sensor electrode
characteristics (e.g., geometry, size, spacing, etc.).
Sensor 42 of test device 14 is disposed within chamber 41 and is
configured as an electrode arrangement for applying an
electrochemical test to determine a property of the blood, such as
a blood glucose level. Finally, input/output contacts 48 of test
strip 18 are electrically connected to sensor 42 and are exposed on
a surface of test device 14 to be removably insertable within
receiver 28 of meter 12 for establishing electrical communication
between test device 14 and meter 12.
Meter 12 comprises housing 22, display 24, control panel 26, and
receiver 28. Meter 12 includes housing 22 for enclosing system
electronics to operate meter 12 and for supporting display 24 and
control panel 26. Control panel 26 enables control of various
functions of meter 12 directed at performing a test and/or
evaluating results of a test on blood sample 18 performed within
test device 14, including calibration of each test device 14 used
with meter 12. Display 24 provides a graphical representation of
the test results and related information to the test consumer. For
example, display 24 can display information related to calibration
of test device 14 with meter 12. Various aspects of meter 12,
including system electronics carried therein, will be described in
further detail in association with FIG. 2.
FIG. 2 is a schematic illustration of a system 50 which
functionally represents system 10. As shown in FIG. 2, system 50
comprises test device 14, including substrate 52, and meter 12.
Substrate 52 of test device 14 comprises test surface 54 with
reagent (R) 44, and circuitry 56. Circuitry 56 comprises sensor 42
and configurable information storage device 58 with calibration
information 46.
As shown in FIG. 2, meter 12 comprises input/output contacts 70,
system electronics 80, which includes among other components,
controller 82 and calibration module 84. Controller 82 directs
various functions of meter 12 including operation of display 24 and
control panel 26, while cooperating with calibration module 84 to
calibrate each test device 14 relative to meter 12.
Test surface 54 of test device 14 is defined by one or more walls
of chamber 41 (FIG. 1) of test device 14 and carries reagents (R)
44 for electrochemical interaction with sensor 42. Information
storage device 58 of test device 14 stores calibration information
(C) 46 for test device 14, and in one embodiment, comprises one or
more electrically conductive elements formed on substrate 52. In
one embodiment, calibration information 46 comprises a value
indicative of a property of one or more chemical reagents on test
device 14. In some embodiments (such as those described in
association with FIG. 8), information storage device 58 of test
device 14 comprises a non-volatile memory portion and is configured
to receive an electrical signal to store calibration information 46
including, but not limited to, a value of a property of chemical
reagent(s), as well as additional information such as date of
manufacture, operating characteristics, electrode characteristics,
etc.
Information storage device 58 is formed, altered, programmed,
and/or configured near the time of manufacture of test device 14 to
store calibration information 46 pertinent for the test strip on
which information storage device 58 resides. Since calibration
information 46 for each test device is present on test device 14,
the calibration information can never be separated from the test
device(s) 14 as each test device 14 carries its own calibration
information. Upon test device 14 being removably inserted into
meter 12, calibration information 46 is automatically communicated
from test device 14 to calibration module 84 of meter 12. This
communication sets meter 12 to operate with appropriate calibration
information 46 unique to test device 14 for achieving an accurate
analyte test in blood-sample 18 (FIG. 1).
As shown in FIG. 3, method 100 is directed to manufacturing a
self-calibrating test device. The systems, or combinations of
systems of FIGS. 1-2 and 4-8 are suitable for performing method
100.
As shown in box 102 of FIG. 3, method 100 comprises forming
circuitry on a substrate of a test device with the circuitry
including a sensor portion and a configurable portion. In one
embodiment, the circuitry is made by depositing metallization
traces over a flexible substrate to form the sensors and
configurable information storage device. This embodiment is further
described and illustrated in association with FIGS. 4-7.
In one embodiment, all of the circuitry formed on the test device
is formed in-situ during the fabrication of the test device. In
other words, the circuitry is formed or deposited directly onto the
substrate through one or more processes such as vapor or plasma
deposition, plasma-enhanced vapor deposition, lamination, etching,
photolithography, electroplating, diffusion, or the like. In
addition other processes can be performed to modify the circuitry.
For example, a laser process can be used to modify and enhance
properties of amorphous silicon.
In some embodiments, the circuitry is made using semiconductor
micro-fabricating techniques including some of those techniques
listed above in which a thin film transistor portion of the
circuitry comprises or couples to a non-volatile memory portion
defining the configurable information storage device for storing
calibration information. This embodiment is further described and
illustrated in association with FIG. 8.
As shown in box 104, method 100 further comprises depositing on the
substrate a chemical reagent of the sensor portion that enables
detection of the blood sample. In one embodiment, these chemical
reagent(s) comprise a chemical reagent that is activated upon
contact of blood sample 18 with the reagents.
As shown in box 106, another aspect of method 100 comprises storing
calibration information in the configurable portion of the
circuitry of the test device. Another aspect of method 100, as
shown in box 108, comprises determining a property of a chemical
reagent on the test device for storage as all of, or part of,
calibration information into configurable portion of the circuitry
of the test device.
One embodiment of a test device is shown in FIG. 4. As shown in
FIG. 4, test device 150 comprises sensor 42, configurable
information storage device 160, and input/output pads 48A/48B.
Configurable information storage device 160 includes an array 162
of conductive elements 164, connective trace 165 (acting as a
conductive element) with first end 166 and second end 168, and
input/output pad 169.
In one embodiment, sensor 42 comprises an electrochemical sensor
electrode pair 42A/42B configured to perform electrochemical
reactions between a blood sample and test reagents within test
device 150. Connective trace 152A is a conductive element
connecting sensor electrode 42A to input/output pad 48A, while
connective trace 152B is a conductive element connecting sensor
electrode 42B to input/output pad 48B.
Configurable information storage device 160 is connected in
parallel to sensor electrode 42B (and its connecting trace 152B)
and is configured for a one-time selection of an impedance among a
range of impedances to produce a characteristic impedance between
input/output pad 48B and input/output pad 169. This characteristic
impedance is indicative of a batch chemistry of the chemical
reagents of test device 150. The impedance of information storage
device 160 is selected by either activating (or deactivating) one
or more of the elements 164 of array 162 near the time of
manufacture of test device 150. Upon a meter accessing the selected
impedance level from test device 150 via input/output pad 169, the
meter is calibrated to test device 150 for the particular
characteristics of the chemical reagent on the test strip. This
calibration occurs automatically, without any affirmative steps by
the consumer, and occurs without the use of a conventional
calibration chip or calibration test strip that is separate from
test device 150 in use with meter 12.
Each element 164 of array 162 of information storage device 160
comprises a conductive element, such as an inductor, capacitor, or
a resistor. Each element 164 is activated or deactivated by
physical alteration of a portion of element 164 to cause either a
short circuit or an open circuit in that element 164. Upon physical
alteration of a select number of elements 164, a characteristic
impedance is achieved (between input/output pad 48B and
input/output pad 169 for array 162) that is indicative of a
property of the chemical reagents of test device 150.
Input/output pad 169 of test device 150, in combination with
input/output pads 48A, 48B are configured to communicate with meter
12 that is configured, at input/output pads 78, to read an
impedance between input/output pad 169 and input/output pad 48B.
Test device 150 also can be used with a conventional meter via
input/output pads 48A, 48B, although the conventional meter will
not be able to read calibration information on information storage
device 160 since conventional meters lack an associated
input/output pad for coupling to input/output pad 169 of test
device 150.
FIG. 5 is a table 170 representing a relationship between an
information storage device (e.g., information storage device 160 of
FIG. 4) and a range of calibration values indicative of a property
of a chemical reagent. To determine calibration information to be
stored in the information storage device, a range of calibration
values is determined that is indicative of a property of the
chemical reagents. This range of values is divided into multiple
portions (e.g., ten portions) so that a range of impedance values
associated with array 162 of conductive elements 164 (FIG. 4)
corresponds to the ten portions of the calibration value range.
This relationship is illustrated in FIG. 5.
As shown in FIG. 5, calibration table 170 comprises row 172 of
calibration values 174, row 180 of the number 182 of altered
elements 164, and row 190 of impedance values 192, which
corresponds to the calibration values 174 and number 182 of altered
elements. The range of calibration values 174 corresponds to a
range of quantitatively measurable characteristics of a chemical
reagent on test device 150. The number 182 of altered elements
shown in table 170 represents the number of conductive elements 164
(FIG. 4) that have been physically altered in information storage
device 160. This number 182, in turn corresponds to a calibration
value 174 shown in table 170 (e.g., 10, 12, etc.), electrically
expressed as an overall impedance value 192 (e.g., A, B, C) shown
in table 170 for array 162 of elements 164 within information
storage device 160. In some embodiments, these relationships
between calibration values and impedance values shown in table 170
also may reflect the order of altered elements. This ordering
parameter is suitable for embodiments described in association with
FIG. 8, in which the array of physically alterable elements
comprises a series of independently addressable fusible links.
As shown in table 170 of FIG. 5, at one end of the calibration
range, all of the conductive elements (e.g., inductor(s)) are
physically altered while at the other end of the calibration range,
none of the conductive elements are physically altered.
Intermediate calibration values are obtained by altering only some
of the conductive elements. Accordingly, the total number of
physically altered conductive elements produces a characteristic
impedance for information storage device (e.g., information storage
device 160 in FIG. 4) that corresponds to a determined calibration
value indicative for a chemical reagent on the test strip.
Finally, in another embodiment wherein the order of altered
elements can be inferred or determined, each altered element
represents one bit of a binary number from a least significant bit
to a most significant bit. Therefore, the number of different
calibration values or buckets equals two raised to the power of N
wherein N is the number of alterable bits.
Techniques for physically altering conductive elements, as well as
various types of conductive elements are described and illustrated
in association with FIGS. 6-7.
FIG. 6 illustrates one of the elements 164 of array 162 (FIG. 4)
configured as an inductor 200. As shown in FIG. 6, inductor 200
comprises inductive coil 202 with arm 204, and each end of inductor
200 connected to connective trace 165 of information storage device
160. Inductor 200 is deactivated by punching or laser drilling
through a portion of the inductor at 206. Inductors 200 of an
information storage device are arranged in series (in substantially
the same arrangement as shown for elements 164 in FIG. 4), and
produce an AC impedance that is determined by the number of
inductor elements 164 that are physically altered (see table 170 in
FIG. 5). In particular, increasing the number of physically altered
inductors 200 as elements 164 produces a higher magnitude inductive
impedance for information storage device 160 and consequently
between input/output pad 48B and input/output pad 169, which is
read by meter 12 (FIGS. 1-2) for calibrating meter 12 to test
device 14.
FIG. 7 illustrates one of the elements 164 of array 162 (FIG. 4)
configured as a capacitor 220. As shown in FIG. 7, capacitors 222
and 224 each have ends 230 for connecting capacitors 222, 224 in
parallel between connective trace 152B of sensor 42 and connective
trace 165 of information storage device 160. Capacitor 222 is
deactivated by physical alteration at location 232. As previously
described in association with FIG. 5, the number of physically
altered capacitors 220 as elements 164 determines a characteristic
impedance for information storage device 160 that acts as stored
calibration information 46 indicative of a property of a chemical
reagent on a test strip. This calibration information 46 is read by
meter 12 for calibrating meter 12 to test device 14.
Array 162 of elements 164 of information storage device 160 (FIG.
4) can include only one type of impedance element (inductor,
capacitor, resistor) or include more than one type, such as a
resistor and an inductor. Moreover, impedance elements 164 can be
connected in parallel or in series, to achieve a desired range of
impedances for using calibration with meter 12 (FIG. 1-2).
In some embodiments, test device 14 is constructed as a substrate
with one or more layers of thin film metallization of conductive
components such as sensor 42 and configurable information storage
device 160 (FIG. 4).
In other embodiments, test device 14 is constructed using
semiconductor microfabrication techniques. For example, FIG. 8 is a
schematic view functionally representing a disposable test device
made according to microfabrication semiconductor techniques,
analogous to technology used in manufacturing flat panel displays.
In particular, system 300 comprises test device 302 and programmer
304. Test device 302 comprises a layered arrangement of substrate
310, circuitry portion 312, electrode portion 314, and fluid
handling portion 316. Programmer 304 comprises electric signal
generator 340 and calibration information (C) 46.
In one embodiment, substrate 310 of test device 302 is constructed
from a plastic, glass, or ceramic material and acts as a carrier
320 to the other portions, while circuitry portion 312 is made of
an amorphous silicon or polycrystalline silicon material.
Circuitry portion 312 of test strip 302 defines non-volatile memory
portion 322 which is configured for storing calibration information
(C) 46 (e.g., a value indicative of a property of chemical reagent,
date of manufacture, electrode characteristics, etc). Calibration
information 46 is written into memory portion 322 via electrical
signal generator 340 of programmer 304 and then is retrievable by a
meter (e.g., meter 12 in FIGS. 1-2) via input/output pads of
electrode portion 314 of test strip 302 that are in electrical
communication with memory portion 322 of circuitry portion 312. In
one embodiment, circuitry portion 312 comprises thin film
transistor (TFT) circuitry. The TFT circuitry includes a portion
for addressing a form of the information storage device such as a
non-volatile memory.
In one embodiment, the storage device includes a number of fusible
links each coupled to independently addressable power transistors.
The particular fusible links that are severed during manufacture of
test device 302 is indicative of information including the proper
calibration information for test device 302. In one embodiment,
each fusible link represents a bit of one or more binary numbers
that represent the information.
In one embodiment, electrode portion 314 of test device 302
comprises a deposited metallization layer made from conductive
trace materials such as copper, gold, platinum, palladium,
graphite, etc, for forming a set 324 of electrode pads,
input/output pads, connective traces, etc.
Fluid handling portion 316 defines a test surface carrying chemical
reagents and is configured for receiving a blood sample for
electrochemical reaction with reagents. Fluid handling portion 316
is disposed generally over electrode portion 314 and comprises a
plastic, photopolymer, or glass material suitable for that
purpose.
In use, test device 302 is constructed and made available for
addition of a chemical reagent onto fluid handling portion 316 of
test device 302. Once a chemical reagent is added to a set of test
devices 302 and a calibration parameter is known that corresponds
to particular batch chemistry for that set of test devices 302,
then that calibration parameter is electrically sent to all test
devices 302 as electrical signal for storage in memory portion 322
of test device 302. In addition, in some embodiments, calibration
information represents other or additional parameters such as
electrode characteristics, date of manufacture, etc. In this way,
each test device 302 stores calibration information (e.g.,
calibration parameters) electronically within the test device 302
so that calibration parameters are inseparable from the test device
302 that is to be used by the patient.
In an exemplary embodiment, circuitry portion 312 includes a number
of power thin film transistors that are each coupled to a fusible
link. During manufacture of test device 302, the power thin film
transistors are used to selectively burn fusible links to encode
information including information indicative of the calibration
parameter. The calibration parameter is represented by a binary
word, and each bit of that word corresponds to one of the fusible
links.
When the device 302 is inserted into meter 12, meter 12 retrieves
electronically stored calibration parameters from memory portion
322 of test device 302 via input/output pads to calibrate meter 12
to test device 302. This calibration occurs automatically and
transparently to the user, independent of and without any separate
manually entered calibration code, separate calibration memory
chip, optical calibration code/color, or separate calibration test
strip (i.e., a test strip used solely for calibration). This can be
done by using the power thin film transistors to couple the fusible
links to circuitry for decoding the binary word.
Embodiments of the present invention enable highly accurate
calibration of disposable analyte test devices with meters by
effectively sidestepping user interaction in calibrating the meter.
In particular, calibration information is electronically stored in
each test device so that no separate calibration chip, alphanumeric
key-entered calibration code, optical calibration code, etc is
required for calibrating a meter to the test device. Moreover, the
calibration information is inseparable from the test strip, as
circuitry defining an information storage device (that stores the
calibration information) is formed directly on or within the
disposable test device. With the calibration information stored in
each test device at or near the time of manufacture, for example,
when the chemical reagents are placed on the test devices,
potential calibration errors are further minimized. Although
specific embodiments have been illustrated and described herein, it
will be appreciated by those of ordinary skill in the art that a
variety of alternate and/or equivalent implementations may be
substituted for the specific embodiments shown and described
without departing from the scope of the present invention. This
application is intended to cover any adaptations or variations of
the specific embodiments discussed herein. Therefore, it is
intended that this invention be limited only by the claims and the
equivalents thereof.
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